Thursday, March 19, 2015

ETLV-2 coupled with an ADEPT deceleration shield on its way the martian surface

by Marcel F. Williams

"As we reported in August 2013, even after the SLS and Orion
are fully developed and ready to transport crew NASA will continue to
face significant challenges concerning the long-term sustainability of
its human exploration program. For example, unless NASA begins a
program to develop landers and surface systems its astronauts will be
limited to orbital missions of Mars. Given the time and money necessary
to develop these systems, it is unlikely that NASA would be able to
conduct any manned surface exploration missions until the late 2030s at
the earliest."NASA Office of Inspector GeneralFebruary 25, 2015

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It is generally agreed by both the Congress and the Executive Branch that sending humans to the surface of Mars, sometime in the 2030s, should be the long term goal of the National Aeronautics and Space Administration (NASA). However, the intermediate destination during the 2020s needed to develop and to mature such space faring capability has been subject to controversy. While some have advocated a return to the lunar surface as a bridge towards Mars, others have argued that the development of a lunar architecture could actually siphon off necessary funds for sending humans to the martian surface.

The extraterrestrial deployment of huge amounts of water will be essential for any interplanetary journey. Even if some future Mars vessels are
xenon fueled solar electric interplanetary vehicles, crewed missions between cis-lunar space and Mars orbit will still require a substantial tonnage water for
drinking, washing, food preparation, the production of air and for mass shielding habitat modules from the dangers of cosmic radiation and major solar events. The most expensive source of water for an interplanetary vehicle within cis-lunar space is from the Earth's deep gravity well. However, water derived from ice in the Moon's polar regions would be a substantially cheaper source since the Moon has a significantly lower gravity well. Water, of course, could also be used for the production of LOX/LH2 propellant
necessary for voyages between cis-lunar space and Mars orbit.

ADEPT payload deployment scenarios for Mars (Credit: NASA)

Because of its thin atmosphere and higher gravity, Mars is a very different world than the Moon. Still,
habitat modules, propellant producing water depots, and mobile ground vehicles that could be
utilized on the surface of the Moon could also be used on the surface of Mars. This could save NASA enormous amounts of money since basically the same surface architecture for the Moon could also be deployed on the surface of Mars. So no new surface infrastructure unique to Mars would not have to be developed.

Vehicles designed to deploy cargoes and crews to the lunar surface could also be used to deploy cargoes and crews to the surface of Mars. But in order to safely deploy cargoes and crews to the martian surface, such vehicles will need to be shielded and decelerated through the thin martian atmosphere through the ADEPT or HIAD technologies currently being developed by NASA.

HIAD and ADEPT
technologies simply use a large expandable heat shield to protect a
spacecraft from the frictional heating of the thin martian atmosphere (100 thinner than the Earth's atmosphere)
while also decelerating the vehicle enough to eventually allow the
vehicle to utilize retrorockets to hover and land on the martian
surface. The weight of these decelerating heat shields approach 50% of
the payload being deployed to the surface. But NASA believes that these
technologies should enable them to deploy as much as 40 tonnes of payload
to the martian surface.

C-ETLV-5 cargo lander and ETLV-2 crew lander for deploying cargoes and crew to the surface of the Moon, Mars, and on the surfaces of the moons of Mars

In July of 1962, NASA invited private companies to submit proposals for the development of a Lunar Module (LM). Seven years later, this lunar landing craft took Neil Armstrong and Buzz Aldrin to the surface of the Moon. Assuming a similar length of time for the development of a new Extraterrestrial Landing Vehicle (ETLV), proposals submitted for an ETLV in 2016 could result in the return of humans to the lunar surface by 2023. Thus, by the 2030's, the ETLV will be a mature landing vehicle ready to deploy humans and cargo to the surface of Mars.

If we assume that NASA's annual human spaceflight related budget remains at approximately $8 billion a year over the next 25 years, then NASA will spend approximately $200 billion over the next quarter of a century on human spaceflight related technology, operations, and activities. $8 billion a year should be enough for NASA to establish a permanent human presence on the surface of the Moon in the 2020s and on the surface of Mars in the 2030s-- if such efforts are prioritized-- especially if NASA is no longer burdened with the $3 billion a year ISS program during the next two decades.

A reusable single staged LOX/LH2 ETLV capable of a round trips between the Earth-Moon Lagrange points and the lunar surface should also be capable of easily transporting crews from the surface of Mars to Low Mars Orbit-- or even all the way to the surface of Mars's inner moon, Phobos. HIAD or ADEPT deceleration shield would, again, be used to deploy the crewed ETLV safely to the martian surface. The cost of developing a crewed lunar landing vehicle has been estimated to be as much as $8 to $12 billion. So over the course of seven years, the cost for developing an ETLV could range from $1.1 billion to $1.7 billion per year. And that's a cost that is certainly affordable with an $8 billion a year human spaceflight related budget.

ETLV-2 at a sintered landing area being refueled with LOX and LH2 for its departure to Mars orbit.

Regolith shielded lunar habitats cheaply derived from SLS propellant tank technology could also be deployed to the martian surface using a lunar cargo lander and a, of course, a HIAD or ADEPT deceleration shield. Regolith shielding a martian habitat to a similar degree as a lunar habitat will be necessary since the level of cosmic ray exposure on the martian surface is not substantially lower than on the lunar surface.

Three habitat modules previously deployed by a C-ETLV-5. The pressurized habitats are shielded with 2 meters of martian regolith contained within the automatically deployed regolith wall. Solar charged batteries are used to provide power for the habitat at night. But nearby nuclear power units buried beneath the regolith will also provide supplementary power for the outpost.

Ionizing Radiation on the Surface of the Moon:

38 Rem - annual amount of cosmic radiation on the Lunar surface during the solar minimum11 Rem - annual amount of cosmic radiation on the Lunar surface during the solar maximumIonizing Radiation on the Surface of Mars:33 Rem - annual rate of cosmic radiation on the surface of Mars beneath 16 gm/cm3 of Martian atmosphere during the solar minimum8 Rem - annual rate of cosmic radiation on the surface of Mars beneath 16 gm/cm3 of Martian atmosphere during the solar maximum

Percentage of water contained in different regions on the martian surface.

Lunar water collecting mobile vehicles using microwaves used to extract water from the regolith at the lunar poles could also be used on much of the martian surface. The water content of the lunar regolith at the lunar poles has been estimated to be approximately 5%. The water content of the martian regolith at the lower latitudes ranges from approximately 1 to 7% depending on the region. But there are large regions near the martian equator that may have regolith with a water content as high as 7%. At higher latitudes, the water content may be as high as 30%. And at the martian poles, the water content could be as much as 70%.

Mobile water tanker and microwave water extraction robot on Mars.

Solar powered WPD-LV-5 water storage and propellant producing unit on the surface of Mars. Additional power can be provided by nearby nuclear power units buried beneath the martian regolith.

Small nuclear power units will probably be necessary to supplement the solar electric power supply at a martian outpost. While batteries and electric flywheels charged during the daytime could provide power for an outpost a night, dust storms could substantially reduce solar electricity for up to a month with dust particles blanketing the solar panels. But small nuclear power units could run 24 hours a day for several years before having to be replaced. So during dust storms, it might be wise for the outpost to contract the solar panels while mostly relying on nuclear power until the storm is over. Such nuclear power units for Mars
should also probably be initially tested on the lunar surface in the
2020s for a few years before they are eventually deployed at a martian outpost in the 2030s.

Nuclear power unit on the Moon with its reactor buried beneath the regolith and its cooling panels above the surface. Such units could also be utilized on the martian surface (Credit: NASA).

"The knowledge that we have now is but a fraction of the knowledge we must get, whether for peaceful use or for national defense. We must depend on intensive research to acquire the further knowledge we need ... These are truths that every scientist knows. They are truths that the American people need to understand." (Harry S. Truman 1948).